From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A275DC1975A for ; Tue, 17 Mar 2020 18:10:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8350D20735 for ; Tue, 17 Mar 2020 18:10:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726704AbgCQSKZ (ORCPT ); Tue, 17 Mar 2020 14:10:25 -0400 Received: from smtp.gentoo.org ([140.211.166.183]:42580 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726388AbgCQSKZ (ORCPT ); Tue, 17 Mar 2020 14:10:25 -0400 Received: from sf (tunnel547699-pt.tunnel.tserv1.lon2.ipv6.he.net [IPv6:2001:470:1f1c:3e6::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: slyfox) by smtp.gentoo.org (Postfix) with ESMTPSA id 913C434F0C3; Tue, 17 Mar 2020 18:10:22 +0000 (UTC) Date: Tue, 17 Mar 2020 18:10:16 +0000 From: Sergei Trofimovich To: Jakub Jelinek Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Andy Lutomirski , x86@kernel.org Subject: Re: [PATCH] x86: fix early boot crash on gcc-10 Message-ID: <20200317181016.0b39bf91@sf> In-Reply-To: <20200317114605.GG2156@tucnak> References: <20200314164451.346497-1-slyfox@gentoo.org> <20200316130414.GC12561@hirez.programming.kicks-ass.net> <20200316132648.GM2156@tucnak> <20200316221251.7b4f5801@sf> <20200317114605.GG2156@tucnak> X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 17 Mar 2020 12:46:05 +0100 Jakub Jelinek wrote: > So, a few comments. > > One thing I've noticed in the command line is that > --param=allow-store-data-races=0 > got dropped. That is fine, the parameter is gone, but it has been replaced > in https://gcc.gnu.org/PR92046 by the > -fno-allow-store-data-races > option. Like the param which defaulted to 0 and has been enabled only with > -Ofast this option is also -fno-allow-store-data-races by default unless > -Ofast, but if kernel wanted to be explicit or make sure not to introduce > them even with -Ofast, I'd say it should: > # Tell gcc to never replace conditional load with a non-conditional one > KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) > +KBUILD_CFLAGS += $(call cc-option,-fno-allow-store-data-races) > in the toplevel Makefile. Yeah, I noticed it yesterday as well and sent out exactly the same change: https://lkml.org/lkml/2020/3/16/1012 I also checked that flag does not change code generation on -O2 for smpboot.c -- Sergei